Field of the Invention
The invention relates to a method and a circuit configuration for identification of a mobile station that is associated with a base station used in particular for identification systems. The mobile station can be an ID transmitter that is carried by a user. One significant field of application is remote controls for vehicle technology, in which the ID transmitter carried on the driver""s body is used to initiate functions on a vehicle, which is acting as the base station. In particular, these functions include unlocking the door, enabling the immobilizer, and/or initiating functions on the ID transmitter, such as status indications.
An autonomous power supply is generally provided in each of the mobile station and the base station. In order firstly to minimize the physical size and weight of such a power supply, and secondly to maximize the operating life as far as possible, the power consumption of the stations should be kept as low as possible. Minimizing power consumption is of major importance, particularly for portable mobile stations.
The prior art shows various methods for minimizing power consumption. One method envisages that the mobile station is provided with a receiver having a particularly low current draw in order to reduce the power consumption, and that the base station transmits only upon operation by the user. A disadvantage in this case is that the current-saving receivers used have a broad bandwidth and are sensitive to interference so that their range is only short; furthermore, the user convenience is only low, since active operation is always required.
Other methods have been developed in which the receiver and transmitter in the base station and the mobile station do not operate continuously, but only at occasional periods (e.g., on a clock cycle). However, in order to ensure that a transmitted signal is received, the reception duration must be relatively long, namely corresponding to the clock interval of the transmitter. Although providing for activation to take place only on demand, namely on operation by the user, is possible, such an addition is disadvantageous for user convenience.
The object of the invention is to provide a method and a circuit arrangement for identification of a mobile station having an associated base station that combines the advantages of low power consumption and high user convenience.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for identification of a mobile station associated with a base station. The method includes the following steps.
Providing a base station having a transmitter and a receive r; and a mobile station having a first low-power mode, a second high-power mode, a transmitter, a receiver, and a clock transmitter connected to said receiver for switching on the receiver on a clock cycle, a wake-up unit connected downstream of the receiver, an evaluation unit connected downstream of the wake-up unit, and a reception interval lengthening unit with an input and an output, the input connecting to the wake-up unit, and the output connected to the clock transmitter.
Generating a clock signal in the base station with the clock transmitter. Generating a clock signal in the mobile station with the clock transmitter that is equal length as the clock signal in the base station. Transmitting periodically based on the clock signal a base station signal from the base station in the low-power mode. Receiving the base station signal in the mobile station being in the first low-power mode. Determining whether the base station signal is being received in the mobile station. Entering the second high-power mode in the mobile station after the base station signal has been received in the mobile station. Lengthening a time period of reception in synchronism with the clock cycle. And, interchanging identification data between the mobile station and the base station.
In accordance with another feature of the invention, the method includes producing a wake-up signal in the mobile station. Then, switching of an evaluation unit to an active state once the second high-power mode has been entered. Then, transmitting an unmodulated request signal from the mobile station once the second high-power mode had been entered.
In accordance with another feature of the invention, in the low-power mode, the reception time period of the mobile station is shorter than the transmission time period of the base station. Preferably, the reception time period of the mobile station is one half to one twentieth the transmission time period of the base station. Most preferably, the reception time period of the mobile station is one-tenth the transmission time period of the base station.
In accordance with another feature of the invention, the clock period is between one and ten seconds. More preferably, the clock period is between four and six seconds.
In accordance with another feature of the invention, the transmission time period is between ten microseconds and one second. More preferably, the transmission time period is between one-hundred microseconds and five milliseconds.
In accordance with another feature of the invention, the interchanging of identification data between the mobile station and the base station includes: transmitting a first identification signal by the base station; receiving and evaluating the first identification signal in the mobile station; reverting to the first low power mode in the mobile station if the result is negative and transmitting a second identification signal if the result is positive, and receiving and evaluating the second identification signal in the base station, the base station reverting to the first low-power mode if the result is negative and carrying out an enable function if the result is positive.
In accordance with another feature of the invention, the interchanging of identification data between the mobile station and the base station is encrypted based on a changing key. Preferably, this key is a count of the clock transmitter.
In accordance with another feature of the invention, the method further includes synchronizing the clock transmitters in the base station and in the mobile station. This synchronizing can includes the following steps: checking that the clock in the mobile station and the clock in the base station are unsynchronized and, if this occurs; transmitting a signal for a time period which is at least as long as the clock period minus the time period of reception; transmitting a synchronization signal between the base station and the mobile station, and setting at least one of the mobile station clock transmitter and the base station clock transmitter with the synchronization signal.
In accordance with another feature of the invention, the synchronization signal is precise with the clock transmitter of the base station.
The invention also encompasses A configuration for identification of a mobile station associated with a base station. The configuration includes the following: a base station having a transmitter and a receiver; and a mobile station having a transmitter and a receiver, and a clock transmitter connected to the receiver for switching on the receiver on a clock cycle, a wake-up unit connected downstream of the receiver, an evaluation unit connected downstream of the wake-up unit, and a reception interval lengthening unit with an input and an output, the input connecting to the wake-up unit , and the output connected to the clock transmitter.
In accordance with another feature of the invention, the wake-up unit has an initial evaluation module.
In accordance with another feature of the invention, the clock transmitter has an oscillating element and a frequency divider unit. The oscillating element can be a quartz crystal.
In accordance with another feature of the invention, the frequency divider unit is a programmable counter.
In accordance with another feature of the invention, the evaluation unit includes a synchronization module connected to the counter and to the receiver designed for loading a corrected count.
In accordance with another feature of the invention, the synchronization module is designed for calculating a correction value from an uncorrected count and a corrected count.
Accordingly, a method for identification of a mobile station that is associated with a base station has a low-power mode and a high-power mode, to which the mobile station changes when a signal is received from the base station.
In the low-power mode, the base station transmits periodically on a clock cycle. That is, a clock in the base station having a specific clock cycle switches a transmitter in the base station periodically on and off based on the clock cycle. The mobile station then receives on the same clock cycle. That is, a receiver in the mobile station switches on and off in a corresponding manner. Also, the mobile station determines whether the signal being received is actually a base station signal from the base station.
If the initial check leads to the result that a base station signal is being received (i.e., the mobile station is near a base station), then the mobile station changes to the high-power mode. In the high-power mode, the time period during which the receiver in the mobile station is switched on is lengthened, preferably by a factor of ten, and synchronized with the clock cycle. In this case, the clock period formed from the sum of the switched-on time and the switched-off time remains constant.
Finally, in the high-power mode, the mobile station and the actual identification is carried out by interchanging identification data between the mobile station and the base station. Because, in the low-power mode, the mobile station just needs to check whether any signal originating from a base station is present at all, the receiver need be switched on only for a very short time. Only when such a signal is being received, need the receiver be switched on for a longer time, in order to allow data to be interchanged.
The initial check avoids changes to the high-power mode being made just due to the reception of interference signals, which would unnecessarily increase the energy consumption. When a base station signal is received, the period for which the receiver is switched on is increased, so that identification data can then be interchanged. Furthermore, the clock cycle process means that the only signals considered are those from base stations which are transmitted in synchronism with the period for which the receiver in the mobile station is switched on.
Splitting the method in two can save energy. Namely, the method can be split into a low-power mode, which is normally used, and a high-power mode, which is used only when required and in which the period for which the receiver is switched on is lengthened. This on the one hand lengthens the operating life and on the other hand allows the transmission power and thus the range to be increased. The method according to the invention furthermore allows the receiver to be designed for high quality and sensitivity and not only for a low current draw.
By suitable selection of the period used for the transmitter and receiver clocks, and the time period per clock cycle for which the transmitter and receiver are switched on, the interchange of identification data, and thus the identification process, can be completed shortly after the mobile station comes into range of the transmitter of the base station. Thus, for example, the central locking system of a car can be opened even before the driver reaches his car and operates the door handle. The convenience of use is thus just as high as with methods using continuous transmission and reception, but with reduced power consumption.
The method according to the invention uses the cycling process not only to reduce the energy consumption, but for pre-selecting the associated base station.
The clock cycle period is expediently chosen to be between one second and ten seconds (1 s-10 s), preferably four seconds to six seconds (4 s-6 s), with a transmission time period between ten microseconds and one second (10 xcexcs-1 s), preferably between one hundred microseconds and five milliseconds (100 xcexcs-5 ms).
In one particularly expedient embodiment of the invention for independent protection, the clock transmitters arranged in the base station and mobile station are synchronized in such away that the process comprises the following steps: checking for an event which indicates an unsynchronized state and; if this occurs, transmitting a signal for a time period which is at least as long as the clock period minus the period for which the receiver is switched on; transmitting of a synchronization signal between the base station and the mobile station, and setting of at least one of the clock transmitters by means of the synchronization signal.
The clock transmitters in the mobile station and the base station must therefore be synchronized at least once, initially, in order to ensure that the mobile station and the base station are operating with the same clock cycle. That is, the receiver in the mobile station switches on when the base station is transmitting. Renewed synchronization may be required if the clock transmitters deviate from one another, for example due to tolerances.
The invention also covers a circuit arrangement having a base station and having at least one mobile station. Each of the base station and the mobile station have a transmitter and a receiver. The mobile station has a clock transmitter which is connected to the receiver, for switching on the receiver on a clock cycle. The mobile station has a wake-up unit connected downstream of the receiver and an evaluation unit connected downstream of the wake-up unit. With the invention providing a base station having a clock transmitter connected to its transmitter, and the mobile station having a reception time lengthening unit whose input is actuated by the wake-up unit and whose output is applied to the receiver, with the wake-up unit having an initial checking module.
In such embodiments, the initial checking module checks an initial signal received by the receiver. The wake-up unit produces a wake-up signal only if the result of the initial check is positive. As a result of which, the evaluation unit then changes to an active state. The evaluation unit may have a switching unit for this purpose, for example in the form of a transistor switch, so that the evaluation unit is not supplied with any current in the low-power mode.
In order to reduce the power consumption further, the initial checking module is expediently designed using analog technology, that is to say without a microprocessor, in order to avoid current-drawing active components as far as possible.
The clock transmitters are expediently designed such that they each have an oscillating element and a frequency divider unit. A quartz crystal is advantageously provided as the oscillating element. It is particularly advantageous for the frequency divider unit to be in the form of a programmable counter. This results in a stable-frequency and easily adjustable clock being produced. The latter is particularly advantageous for synchronization of the clock transmitters. To this end, the evaluation unit is expediently provided with a synchronization module, which is connected to the counter and is designed for programming in a corrected count.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and configuration for identification of a mobile station associated with a base station, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.